Process of roasting ores



A ril 25, 1933. I -A. J. QUENEAU 1,905Q604 PROCESS OF ROASTI'NG ORESFiled June 25', 1951 .4: U a GI 7 3 l I ALL 51 w HI INVENTOR av g a rATTORNEYS Patnted' 1 r.25 1 33 f.

UNITE-o STATES- PATENT Ol fFlCEf. 7

mav ns LEO Juan QUENEAU, ornnw YORK, Y

rnocriss or 'noasrme onus Application filed June 25,

This invention relates to "metallurgy and more particularly to methodsof treatlng ores and metal bearing materialsto facilitatethe recovery ofthe metal bearing constituents thereafter recovered from the roastedre'sidues in any convenient'manner.

Inthe oxidizing of zinc sulphide ore, it is customary to pass the orethrough a roaster in order to liberate the sulfur and to bring about. atransformation of the zinc sulphide to zinc oxide so that metallic zinccan be re-v covered the'refromby lmown methods of pyro-metallurgy. V i

- In the oxidizing of zinc sulphide ore, it has been found thatanexcessive heat is developedat certain places within theroastingiurn'aces which causes a detrimental fusing ofthe ore and bringsabout an agglomeration of the charge. This solidification oragglomeration interferes very materially with the operation of thefurnace 'and requir es frequent shutdownsfor the purpose'of breaking upthe charge. Air cooling at such zones has been resorted to. This isobjectionable 'as it increases the volume of outgoing gases and alsoincreases the dust carryingcapacity thereof."

It is one of the objects of the present invention. to eliminate thisdetrimental fusing of the zinc sulfide ores during the oxidizing of the-same.-

Another object of the present invention is Q to improve the methodofoxidizing zinc sul- Another object of the. present invention is toprovide an improved type of ore roasting apparatus.

will become apparent as the invention is'more fully disclosed. Inaccordance with the objects of the present invention I have foundthatthisdetri mental heating of the ore usuallypcc'urs'with Theefiluent.ly large quantity of dust particles whichare reintroducing of the dust1931; "Serial in. 546,892.

in the furnace between the fifth and seventh heartlis (counting from thetop) in astand- -ard type of' 16 hearth roasting furnace customarilyused.

' I have 'also found that thisv detrimental 55 heating may be overcomeby: introducing .within the furnace and upon the hearth or I hearthswherein this 1 detrimental fusing occurs, a proportion of inertmaterial, ref-' erably of relatively high heat absor ing value,thereby'ofisetting the tendency of the ore'to liberate the excessiveheat energy at this point.

furnace gases carry a relative-- comprised of a relatively highproportion of zinc sulfate. To-convert zinc sulfate into zinc oxide and.sulfur oxide products arelatively large quantity of heat must be appliedthereto. I propose therefore to recover the dust product of the-efiluentgases of the furnace and to return-the same to the furnace at the zonewhere excessive heating usually takes place thereby utilizing theendothermic reaction of the thermal decomposition of-the zinc sulphatecontentof the dust product to bring about a cooling of the oreunder.treat- 7 ment at the critical zone; Before further disclosing thenature'and scope of the present I invention, reference shouldbe made tothe following drawing wherein; The figure is a vertical longitudinalsection through a roasting furnace suitable for I carrying out themethod of the invention,

' the view also diagrammatically showing cer- 5 tain related apparatus'for the collecting and product into the hot zone of the furnace. vReferring in detail to the drawing, 10'represents a roasting furnace ofknown construction which is usually provided with a J plurality ofsuperimposedshelf-like hearths 12' having central openings 14:. Stirringarms 16 carried by a centrally disposed ro- These and other objects andadvantages tatable shaft 18 serve to feed the pulverized ore along-thehearths. Fuel such as natural gas, clty gas, oil. or the like may be.,introduced within the" furnace through a suitable burner 22.

the excessive heating takes place in the zone between the fifth andseventh hearth.

The heated and oxidizing gases arising in the furnace from burner 22carry off a dust product containing a substantial proportion of zincsulphate (ZnSO These gases and the entrained dust are taken off at thetop of the roasting furnace through a pipe 26 and led to a suitable dustseparator 28. The dust is trapped in the separator and flows through apipe 30 to a bin 31 and thence to a screw conveyor 32 which introducesthe dust containing the zinc sulphate onto the hearth located at thepredetermined critical zone.-

A pipe 34 connected to the dust collector carries oif'the sulphurdioxide to a suitable apparatus (not shown) for the recovery ofsulphuric acid. Y

The zinc sulfate content of the dust thus introduced is thermally decompsed by the heat energy of the furnace to form zinc oxide and sulfuroxides compounds. This reaction is endothermic innature and requires arelatively high temperature approximating 770 C. In addition the dustparticles because they are relatively cold have a distinct coolingeffect on the temperature of the charge independent to the endothermicther; mal decomposition reaction.

From the foregoing it will be readily apparent that according to mynovel method the cooling of the charge ofore und er treatment is broughtabout solely by 1ntroduct1on of the dust product recovered during normaltreatment and withouttlie introduction of any cooling air. Thus thecooling effect is secured without increasing the volume of outgoinggases and consequently without multiplying the dust carrymg capacity ofsuch gases. The advantages which accrue as a result of the improvedmethod will be readily appreciated by those skilled in the art.

While I have described with great particularity certain specific stepsin the preferred method it is not to be construed that I am limitedthereto and the detailed description is to be interpreted in 'anillustrative rather than a limiting sense since various modificationsmay be made by those skilled in the art without departure from the scopeof the invention as defined in the appended claims.

What is claimed:

1. In the roasting of ores, the method of controlling the temperature ofthe roast which comprises adding at an intermediate pointin'the roastingprocess where the temperature is excessive increments of thermallydecomposable material of relatively high heat absorbing capacity.

2. In the roasting of ores, the methodofcontrolling the temperature ofthe roast which comprises adding at an intermediate point in theroasting process where the temperature is excessive during the roastingoperation increments of thermally; decomposable 'material of relativelyhigh heat absorbing capac- 1 3.- In the roasting of zinc sulfide ores,the method of controlling the temperature of the roasting operationwhich comprises adding at an intermediate point in the roasting processwhere the temperature is excessive incre- V ments of thermallydecomposable material of relatively high heat absorbing capacity.

. 4. In the roasting of zinc sulfide ores, the method of controlling thetemperature of the roasting operation which comprises adding at anintermediate point in the roasting process Where the temperature isexcessive increments of zinc sulfate.

5. In the roasting of zinc sulfide ores, the method of controlling thetemperature of the roasting operation which comprises adding at anintermediate point in the roasting process where the temperature isexcessive increments of material comprised in part of zinc sulfate.

6. In the roasting of zinc sulfide ores the method of controlling thetemperature of the roasting operation which comprises adding to the oreat a predetermined point in the furnace where the temperature during theroasting becomes excessive, a proportion of a material comprised atleast in part of thermally decomposable material of relatively high heatabsorbing capacity. 4 v

7. In the roasting of zinc sulfide ores the method of controlling thetemperature of the roasting operation/which comprises adding to the oreat a predetermined point in the furnace where the temperature during theroasting becomes excessive, a proportion of a material comprised atleast in part of zinc sulfate.

8. In the roasting of zinc sulphide ore the method which includes thestep of utilizing zinc sulphate (ZnSO to exert a cooling action on theore at a predetermined point in the roasting furnace where-the roastingtemperatures become excessive.

9. A method of roasting zinc sulphide ore. which comprises feeding theore in a finely divided state through an atmosphere of hot oxidizinggases, collecting the resulting dust product containing zinc sulphate(ZnSO.) and returning said duct product to the ore under treatment at apredetermined zone where the roasting temperatures become excessive soas to utilize its endothermic reacmethod which comprises feeding thefinely divided ore successively over a plurality of hearths of aroasting furnace, subjecting the ore to the heat of'reaction of anoxidizing gas in the roasting furnace,carrying off the resulting gasesand a fine dust product comprised at least in part of zinc sulphate,zinc oxide and gangue, collecting such dust product and reintroducing itat a predetermined zone of the furnace where the roasting temperaturebecomes excessive to effect a cooling of the ore under treatment in saidzone.

11. In the roasting of zinc sulphide ore, the method which comprisesfeeding finely divided ore gradually over the heart-hs of a roast ingfurnace, subjecting the ore to an atmosphere of oxidizing gases in saidfurnace, collecting a dust product carried off with the outgoing gaseswhich product includes a. substantial percentage of zinc sulphate, andmixing such dust product with the ore under treatment at a predeterminedzone within the furnace where the roasting temperature become excessiveso as to utilize the endothermic reaction of the zinc sulphate contentin the dust product to effect a reduction of temperature of the oreunder treatment in said zone.

In witness whereof, I have hereunto signed my name.

AUGUSTIN LEON JEAN QUENEAU.

